1. Field of the Invention
The present invention relates to a mechanical jack for use in connection with lifting jacks. The mechanical jack has particular utility in connection with mechanical model jacks actuatable by a twistable handle.
2. Description of the Prior Art
Mechanical jacks are desirable for raising and lowering objects such as cars. A need was felt for a mechanical jack that could be shown with model cars such that the jack could be actuated by the twisting of the handle.
The use of lifting jacks is known in the prior art. For example, U.S. Pat. No. 5,201,494 to Lundman discloses a hydraulic jack and pump usable therewith that includes a linkage movable from a first position to a second position for engaging and elevating a load. A hydraulic ram coupled to the linkage for moving the same toward its second position upon the application of fluid pressure, and a pump coupled to the hydraulic ram for applying fluid pressure thereto. The pump includes a piston operable for delivering a first quantity of hydraulic fluid to the ram through a first path at a first pressure. The pump delivers a second quantity of hydraulic fluid to the ram through a second path at a second pressure. The first quantity of hydraulic fluid being substantially larger than the second quantity and the first pressure being substantially lower than the second pressure. A pressure relief valve is coupled to the first path for venting when the back-pressure from the hydraulic ram exceeds a predetermined value. The linkage is advanced at a first higher speed from its first position to engagement with the load and a second lower speed with increased force after the load has been engaged and elevated for elevating by the same. However, the Lundman '494 patent does not have a twisting handle that actuates a jack by engaging ratcheting teeth.
Similarly, U.S. Pat. No. 4,018,421 to Tallman discloses a portable lifting jack that has a base supported on wheels, and elevating linkage, a hydraulic ram operating with the linkage and a handle for pressurizing and releasing the hydraulic ram. An integral block of rectangular configuration serves a multiple purpose of providing a reservoir for hydraulic fluid, mounting the ram, mounting the pump, and providing exteriorly drilled bores for all the hydraulic acitivity. However, the Tallman '421 patent does not have a twisting handle that actuates a jack by engaging ratcheting teeth.
Lastly, U.S. Pat. No. Des 442,345 to Lee et al discloses a trolley jack that has a curved body for not scratching items to be lifted. However, the Lee et al '345 patent does not have a twisting handle that actuates a jack by engaging ratcheting teeth.
While the above-described devices fulfill their respective, particular objectives and requirements, the aforementioned patents do not describe a mechanical jack that allows mechanical model jacks that can be actuated by a twisting handle. The Lundman '494, Tallman '421 and Lee et al '345 patents make no provision for have a twisting handle that actuates a jack by engaging ratcheting teeth.
Therefore, a need exists for a new and improved mechanical jack that can be used for mechanical model jacks that can be actuated by a twisting handle. In this regard, the present invention substantially fulfills this need. In this respect, the mechanical jack according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in doing so provides an apparatus primarily developed for the purpose of mechanical model jacks that can be actuated by a twisting handle.